how to fix P0304 code in Volkswagen Passat B8 (2015-2022)

Learn how to diagnose and fix P0304 cylinder 4 misfire in Volkswagen Passat B8 (2015-2022). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before starting work.

2. Inspect and Replace the Spark Plug

• Tools Required: Socket set, torque wrench.
• Remove the ignition coil from cylinder 4.
• Remove the spark plug using a spark plug socket.
• Inspect the spark plug for wear and carbon buildup; replace if necessary.
• Install the new spark plug to the manufacturer's specified torque (typically around 15-20 Nm).

3. Test and Replace the Ignition Coil

• Check the ignition coil for proper resistance using a multimeter (consult the service manual for specifications).
• If defective, disconnect the wiring harness and remove the ignition coil.
• Install a new ignition coil and reconnect the wiring harness.

4. Inspect and Clean/Replace the Fuel Injector

• Remove the fuel rail to access the injector for cylinder 4.
• Inspect the injector for clogs; use a fuel injector cleaner if it appears dirty, or replace it if necessary.
• Reinstall the fuel injector and fuel rail, ensuring proper sealing and connections.

5. Perform Compression Test

• Connect the compression tester to cylinder 4.
• Crank the engine and record the compression reading.
• If the compression is below specifications, further engine disassembly may be required for repairs.

6. Reassemble and Finish

• Reconnect all components removed during the repair.
• Reconnect the battery.
• Clear the fault codes using the OBD-II scanner.